1. Field of the Invention
This invention generally relates to a sprocket assembly for a bicycle. More specifically, the present invention relates a sprocket assembly that is lightweight relative to conventional designs.
2. Background Information
In recent years, bicycle component manufacturers have been manufacturing bicycle transmissions that have more available speeds to the rider. As the available speeds in the bicycle transmission increases, the number of sprockets installed on the rear wheel also usually increases. As a result, the weight of the bicycle has increased. Thus, there is a desire to reduce the weight of the bicycle. In other words, in pursuit of a faster riding speed, it is desirable to reduce the weight of all kinds of parts of the bicycle.
Various attempts have been made in order to reduce the weight of a multiple sprocket assembly. For example, some multiple sprocket assemblies use a spider (sprocket support), which supports a plurality of ring-shaped sprocket wheels. By using a spider, a light metal such as aluminum, etc., is generally used for the spider, while various types of steel materials are used for the sprockets to provide adequate strength. One example of a multiple sprocket assembly that uses a spider is disclosed in U.S. Pat. No. 6,102,821 (assigned to Shimano Inc.). While this construction reduces the overall weight of the sprocket assembly, it requires a pair of special spiders to be manufactured.